1. Field of the Invention
This invention generally relates to a communication apparatus which is powered by a rechargeable battery, and, in particular, to a battery-operated communication apparatus, such as a facsimile machine powered by a battery, which may be mounted on a vehicle, such as an automobile.
2. Description of the Prior Art
It is often desired that a communication apparatus, such as a facsimile machine or a data communication machine, be movable in location. For example, such a communication apparatus is sometimes desired to be carried on a vehicle, such as an automobile, so that it can transmit or receive data to or from another communication apparatus, for example, at a central station. In such a case, the power required to operate the communication apparatus carried on the vehicle must be supplied from a battery which is also mounted on the vehicle. Since the vehicle is normally equipped with a rechargeable battery, it is common sense to use such a rechargeable battery to supply power to the communication apparatus.
As well known in the art, such a rechargeable battery is kept charged by a power generator which is driven to rotate by an internal combustion engine of the vehicle. Thus, while the engine of the vehicle is in operation, the power may be constantly supplied to the communication apparatus because the battery is recharged by the power generator whenever its power storage has decreased beyond a predetermined level.
In the case of a communication apparatus, such as a facsimile machine or a data communication apparatus, there is normally provided an automatic reception function for receiving transmitted data automatically. In such a case, the communication apparatus includes a call detector which constantly receives a minute amount of power from the battery, and the rest of the apparatus is not powered during the stand-by mode during which neither transmission nor reception is carried out. Upon receipt of a call from a remote source station, the call detector sends a detection signal to a main controller of the communication apparatus so that the entire apparatus becomes powered to get ready for receiving data transmitted. The power supplied to the entire apparatus is much larger than the power supplied to the caller detector. In addition, when the apparatus operates in a transmission mode or reception mode, its reading unit or recording unit is normally driven so that there is required more power to be supplied.
If such a communication apparatus equipped with an automatic reception function is mounted on a vehicle, the battery may be used excessively and become dead if the vehicle is left in a parking lot and thus its engine is not operating. In this case, the battery is not capable of supplying enough power to get the engine started even if the ignition key of the vehicle is switched on, which is disadvantageous. On the other hand, if the automatic reception function of the communication apparatus is made inoperative while the engine is not in operation, a chance of receiving transmitted information may be lost, and, thus, this is not acceptable, either. It is not conceivable to keep the engine running at all times because there is a possibility of danger and it will amount to wasteful consumption of gasoline.